1. Field of the Invention
This invention relates to web cutters and cutter feeding systems.
2. Background Information
The use of continuous web for high speed printing operations, including print-on-demand and direct mail applications has become extremely popular. A continuous web, held on a driven roll, is driven through a series of stages in which printing and other embellishments are applied in the form of pages or sections of the web. The web can be driven through various printers and other web utilization devices while remaining in its continuous form. Web is generally driven through these utilization devices using a conventional tractor pin feed method in which perforated, pin feed strips along opposing side edges of the web are engaged by tractor pin feed units, or the web can be driven using a pinless feed method and drive, such as that described in U.S. Pat. No. 5,967,394 entitled METHOD AND APPARATUS FOR PINLESS FEEDING OF WEB TO A UTILIZATION DEVICE, by H. W. Crowley et al., the teachings of which are hereby incorporated herein by reference.
At a predetermined stage in the overall web-handling process, the continuous web may be fed from a driven source roll or other upstream source device to a web cutter. The cutter uses a moving knife (typically a guillotine, rotary or sliding type blade) to divide the web widthwise (e.g. laterally or transversely to the direction of movement) into individual sheets of predetermined size. As sheets are cut, they are directed downstream to further utilization devices that may include justifiers, folders, further printers, stackers or sorters. The cutter, or another utilization device, may also include a slitter that divides the web lengthwise into two or more side-by-side ribbons in order to maximize throughput by allowing the cutting and downstream-processing of two or more side-by-side sheets concurrently. The sheets can be subsequently stacked or otherwise handled in a side-by side fashion. In some implementations, a downstream justifier can include appropriate mechanisms for merging the slit sheets into a single feed path. Alternatively, the sheets can be merged prior to cutting, and then cut one-atop-the-other.
Conventional and currently available cutters are limited by a variety of disadvantages. Often, their infeed arrangement from a source involves a tortuous feed path in order to carefully regulate the location of web presented to the cutter. In high-speed operation, the cutter must move quickly and violently to divide the sheets. The tortuous web feed path, when maintained in a moderately tensioned state, is subjected to significant shock by the action of the cutter, which may lead to inaccuracy in the size of cut sheets—as the web is susceptible to sudden jerks during cuts. Similarly where the web is paused to receive a cut from, for example a guillotine-style knife cutter, the drive rate of the cutter section may vary from that of the infeed section. In addition, the tortuous infeed path is difficult to thread during loading and, once threaded, may form a permanent serpentine deformation in the web when it is allowed to stand in the cutter for any significant waiting time. This deformation can adversely affect feeding into downstream devices as the web presents an undesirable curl to the cutter, justifier, etc.
In addition, many cutters must be carefully adjusted at a number of different, discrete locations in order to ensure that the web is properly guided along its side edges. This is often accomplished by the operator through simple and inaccurate manual and visual techniques that may lead to misalignment between guides and off-center feeding. This adjustment problem is exacerbated where a cutter is designed to feed either pin-feed or pinless web. It is, thus, desirable to provide a system and method for cutting continuous web that addresses the various above-described limitations.